Two lumen hemodialysis catheter

ABSTRACT

A dual lumen hemodialysis catheter. The catheter includes a tube having a circular external cross section which is rotatably received within a fitting. The fitting may be attached to the patient by sutures or the like and rotatably mounts the tube of the catheter. Stop means are provided on opposite sides of the fitting preventing the tube of the catheter from moving longitudinally relative to the fitting. The catheter may be rotated relative to the fitting in order to readjust the rotational position of the tube inside the patient&#39;s blood vessel without longitudinal movement of the tube. The catheter is cut off at its distal end perpendicularly to the length of the tube in order to define the mouth of one lumen. The tube is tapered from the cut off distal end to a point proximal of the distal end, said point being approximately 3 cm from the distal end. The taper of the tube defines at least a portion of the mouth of the second lumen.

BACKGROUND OF THE INVENTION

The present invention is related generally to intravenous catheters andmore particularly to a catheter particularly adapted for hemodialysis.

DESCRIPTION OF THE PRIOR ART

There is available a number of catheter designs for use in thesimultaneous introduction of fluid into the body and withdrawal of fluidfrom the body. Such catheters are particularly useful in hemodialysis.Two such designs are illustrated in the U.S. Pat. No. 4,180,068 Jacobsenet al. and the U.S. Pat. No. 4,134,402 to Mahurkar. The devices of eachof these patents are designed in such a manner as to promote insertionof the device into the vessel. Thus, the Mahurkar device includes abeveled edge which slopes away from the needle to facilitate insertionof the needle. Also, the Jacobsen device has a built in trocar forpiercing in order to insert the catheter. Such features do notnecessarily aid in proper operation of the catheter when inserted and inplace and in some instances may interfere with such proper operation. Itis desirable that the catheter be designed in such a fashion as toreduce to as low an amount as possible the mixing of the dialyzed andthe undialyzed blood. It is also desirable that the catheter be designedso as to promote and permit free flow of blood into and out of thecatheter.

SUMMARY OF THE INVENTION

One embodiment of the present invention might involve a catheterincluding a tube having a circular external cross section. A fitting isrotatably mounted on the tube so as to surround the circular crosssection. The tube is rotatable about its axis relative to the fitting.The fitting has a projection which is adapted to be attached to the skinof the patient whose blood vessel is percutaneously catheterized by thecatheter. There is also provided stop means fixed to the tube onopposite sides of the fitting and preventing the tube from movinglongitudinally relative to the fitting. The above described structuremakes possible the catheter being rotated relative to the fitting inorder to readjust the rotational position of the tube inside the bloodvessel without longitudinal movement of the tube and without separatingthe attachment of the projection to the skin.

Still another embodiment of the invention may additionally include apair of side by side lumens in the tube with one of the lumens extendingall the way to the distal end of the catheter. The catheter is cut offat the distal end perpendicularly to the length of the tube in order todefine the mouth of one lumen. The tube is tapered from the cut offdistal end to a point proximal of the distal end, said point beingapproximately 3 cm from the distal end. The taper of the tube defines atleast a portion of the mouth of the second lumen.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation of a two lumen hemodialysis catheterembodying the present invention.

FIG. 2 is a enlarged section taken along the lines 2--2 of FIG. 1 in thedirection of the arrows.

FIG. 3 is an enlarged side elevation of the portion of the structuremarked 3 in FIG. 1 with areas broken away to show the internalconstruction by a sectional view taken axially of the catheter.

FIG. 4 is a top plan view of the distal end of the catheter with theview being taken at 90° to the view of FIG. 1.

FIG. 5 is an enlarged side elevation of a portion of the structureillustrated in FIG. 1.

FIG. 6 is a view taken along the line 6--6 of FIG. 5 in the direction ofthe arrows.

FIG. 7 is a view taken along the line 7--7 of FIG. 1 in the direction ofthe arrows and showing a plastic clamp forming a part of the structure.

DESCRIPTION OF THE PREFERRED EMBODIMENT

For the purposes of promoting an understanding of the principles of theinvention, reference will now be made to the embodiment illustrated inthe drawings and specific language will be used to describe the same. Itwill nevertheless be understood that no limitation of the scope of theinvention is thereby intended, such alterations and furthermodifications in the illustrated device, and such further applicationsof the principles of the invention as illustrated therein beingcontemplated as would normally occur to one skilled in the art to whichthe invention relates.

Referring more particularly to the drawing, there is illustrated a twolumen hemodialysis catheter 10 which includes a tube 11 having anexternal circular cross section 12 as shown, for example, in FIG. 2.Even though the external configuration of the tube is cylindrical, thetube has a pair of lumens 15 and 16. The lumen 15 is separated from thelumen 16 by a wall 17. The lumen 16 has a generally elliptical crosssection, whereas the lumen 15 is generally of less-than-half-moon shapeand generally curves around the lumen 16 and has a somewhat larger crosssectional area than the lumen 16. In one specific embodiment of theinvention, the dimension 16A of the lumen 16 is 0.055 inches and thedimension 15A of the lumen 15 is 0.068 inches. Such two lumens tubing isavailable commercially and may be purchased, for example, from SabinCorporation of 617 South Curry Pike, P.O. Box 788, Bloomington, Ind.47401 under the model designation PUTL-12.

In order to manufacture the distal tip of the catheter of the presentinvention, the large lumen 15 is basically cut off for a 3 cm distance.Thus the distance 20 is 3 cm. This cutting off procedure produces ataper from the point 21 to the point 22 which point is approximately 2cm from the distal tip 23 of the catheter. The catheter is cut off atthe distal end 23 perpendicularly to define the mouth of the lumen 16.

The catheter of the present invention is placed into the blood vessel bythe use of the Desilet-Hoffman procedure. The catheter of the presentinvention and specifically the tube 11 is made out of a relativelyflexible plastic material so that it does not have sufficient stiffnessand rigidity nor sharpness on its own to be inserted into the bloodvessel. The procedure for inserting the catheter into the blood vesselinvolves the use of a needle and a wire guide. After the needle has beeninserted into the blood vessel, the wire guide is placed through theneedle into the blood vessel. Next the needle is removed from the wireguide and a dilator with an overlying sheath is slid over the wire guideinto the blood vessel. The sheath may be one such as the sheathdisclosed in the Osborne patent, U.S. Pat. No. 4,306,562 and reissueapplication Ser. No. 443,321. The above description of theDesilet-Hoffman procedure is illustrated in FIGS. 3-10 of U.S. Pat. No.4,306,562 and reissue application Ser. No. 443,321. The wire guide anddilators are removed from the sheath and the catheter of the presentinvention is inserted into the sheath into the blood vessel. Lastly thesheath is removed from the catheter by tearing it longitudinally asdescribed in U.S. Pat. No. 4,306,562 and reissue application Ser. No.443,321.

The catheter 10 further includes a fitting 30. The fitting 30 is shownin detail in FIGS. 5 and 6 as having a pair of projections 31. When thepresent catheter is in use, the projections 31 are sutured to the skinof the patient by use of the apertures 32. Stop means 35 and 36 areprovided on opposite sides of the fitting 30 so as to prevent the tubefrom moving longitudinally relative to the fitting. The stop means 36consists of a tubular length of shrink tube 40 as well as an additionalshorter length of shrink tube 41. The shrink tube 41 is mounted upon thetube 11. The shrink tube 40 is mounted upon the tube 41 and surroundsthe portion 42 of the fitting as well as tubes 45 and 46 which areconnected to the lumens 15 and 16 by metal tubes 50 and 51. The tubes 50and 51 are telescoped within the lumens 15 and 16 and the tubes 45 and46, respectively. All of the structure, except for the portion of theshrink tube 40 that surrounds the collar 42 of the fitting 30, issuitably attached together by superglue and urethane bond. The portionof the shrink tube 40 that surrounds the collar 42 of the fitting 30allows rotation of the tube 11 within the fitting 30 but does providesome resistance to such rotation by the engagement of the shrink tube 40with the collar 42.

There is also provided suitable clamps 52 and 55 for closing off theflow of fluid through the tubes 45 and 46, respectively. These clampsare identical and are formed of flexible plastic material.Representative clamp 55 is shown in front elevation in FIG. 7. Mountedon the ends of tubes 45 and 46 are female Luer lock adapters 60 and 61threadedly mounted thereon for coupling the tubes 45 and 46 to adialysis machine. The Luer lock adapters permit Luber lock attachment.Such adapters 60 and 61 are commercially available from CookIncorporated, 925 South Curry Pike, Bloomington, Ind. 47402.Alternatively, other coupling means may be used.

It will be evident from the above description that this inventionprovides an improved catheter for use in hemodialysis. The catheterpermits easy adjustment by the user because all that is required tochange the orientation of the catheter in the blood vessel is rotationof the catheter relative to the fitting 30 causing the distal end of thecatheter to be reoriented relative to the blood vessel. It will also beevident from the above description that the catheter of this inventionhas a different construction of its distal tip. This differentconstruction has been found to produce a very substantially improvedoperation of the catheter when used for hemodialysis.

In hemodialysis the lumen 16, i.e., the distal port is used to injectthe dialyzed blood. The lumen 15, i.e., the proximal port is used towithdraw the undialyzed blood. In conventional catheters used forhemodialysis, there is a considerably amount of mixing between thedialyzed blood and the undialyzed. Thus, users report that inconventional hemodialysis catheters about 20 to 25% of the bloodwithdrawn is dialyzed blood. With the use of the present design,evaluators have reported 3.1% of the blood withdrawn is dialyzed blood.

It should also be mentioned that the cutting off procedure mentionedabove of the large lumen 15 increases the flexibility of the tip of thecatheter. Although there is no present direct scientific evidence tosupport the following, it is believed that increased flexibility reducesthe possibility of the tip eroding through tissue. It should also benoted that the present design has no side ports and instead has twostraight through lumens which open at their distal ends either directlyaxially or at least partially in an axial direction, that is,longitudinally of the catheter. It is believed that such straightthrough lumens with no side ports reduces turbulence and results inlower recirculation percentage although there is presently no directscientific evidence to support such conclusion.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, the same is to be considered asillustrative and not restrictive in character, it being understood thatonly the preferred embodiment has been shown and described and that allchanges and modifications that come within the spirit of the inventionare desired to be protected.

What is claimed:
 1. A catheter comprising a tube having a circularexternal cross section, a fitting rotatably mounted on said tube so asto surround said cross section, said tube being rotatable about its axisrelative to said fitting, said fitting having a projection adapted to beattached to the skin of a patient whose blood vessel is percutaneouslycatheterized by said catheter, and stop means fixed to said tube onopposite sides of said fitting and preventing said tube from movinglongitudinally relative to said fitting, whereby said catheter can berotated relative to said fitting in order to readjust the rotationalposition of said tube inside the blood vessel without longitudinalmovement of the tube and without separating the attachment of theprojection to the skin, wherein said catheter is a two lumenhemodialysis catheter, wherein said lumens are side-by-side, saidcatheter having a distal end, one of said lumens extending all the wayto the distal end of said catheter, said catheter being cut off at saiddistal end perpendicularly to the length of said tube to define themouth of said one lumen, said tube being tapered from said cut offdistal end to a point proximal of said distal end, said point beingapproximately three centimeters from said distal end, said taper of saidtube defining at least a portion of the mouth of said second lumen. 2.The catheter of claim 1 wherein the cross sectional area of the onelumen is greater than the cross sectional area of the other lumen. 3.The catheter of claim 1 wherein the cross sectional area of said onelumen is elliptical and the cross sectional area of said other lumen isgenerally of less-than-half-moon shape and generally curves around theone lumen.
 4. The catheter of claim 1 wherein said lumens are separatedfrom one another by a wall, said one lumen having a cross sectional areawhich is elliptical, said other lumen being of generallyless-than-half-moon shape and generally curving around the one lumen,the central dimension across said one lumen taken perpendicular to saidwall being 0.055 inches, the central dimension across said other lumentaken perpendicularly to said wall being 0.068 inches.
 5. The catheterof claim 1 in which the lumens open at the distal end at least partiallyin the direction of the length of the tube.
 6. The catheter of claim 4wherein the cross sectional area of the one lumen is greater than thecross sectional area of the other lumen.
 7. The catheter of claim 7 inwhich the side walls of the tube are continuous and the only openingstherein between said fitting and said distal end are said mouths.
 8. Thecatheter of claim 5 having a solid wall construction all the way to bothlumen mouths.